Process of preparing ferrous chloride from mixed chlorides of iron and nickel



United States Patent PROCESS OF PREPARING FERROUS CHLORIDE FRggIE MIXED CHLORIDES OF IRON AND NI L Marion Ernest Graham, Parma, and Edward A. Beidler, Columbus, Ohio, assignors, by mesne assignments, to Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey No Drawing. Application June 17, 1952, Serial No. 294,058

1 Clm'm. (Cl. 2387) The present invention relates to liquid phase separation of FeClz and NiClg to produce metallic nickel and substantially pure ferrous chloride.

As such, the present invention is related to our copending applications, Serial Nos. 160,821 and 160,822, both filed May 8, 1950, now U. S. Patent 2,677,593 and U. S. Patent 2,677,606 respectively, each issued May 4, 1954 and relating respectively to separation of ferrous chloride from material containing ferrous chloride and nickel chloride in the solid and/or liquid phase, and separation of ferrous chloride from material consisting essentially of ferrous chloride and metallic nickel. The present invention distinguishes from these two copending applications, in that application Serial No. 160,821 g is limited to removal of the ferrous chloride from the reaction zone by vaporization of the ferrous chloride, the metallic nickel remaining behind and being separately removed. The present application is now limited to the remaining metallic constituents being physically separated from the reaction zone to leave therein a bath of substantially pure FeCl-z.

The present application distinguishes from application, Serial No. 160,822 in that the starting material in Serial No. 160,822 contains metallic nickel and substantially no nickel chloride and it is desired to prevent any conversion of the metallic nickel to nickel chloride; while in the present application the starting material contains nickel chloride, which it is a principal purpose of the process to convert to metallic nickel.

The present application is one of a group of seven co-pending applications, all the inventions of the same inventors, four of these cases relating to nickel and reactions involving nickel and the other three relating to cobalt and reactions involving cobalt. The cases may be compared and distinguished as follows:

a. Ser. No. 160,821, filed May 8, 1950, now U. S. Patent 2,677,593, issued May 4, 1954, relates to treating a starting material in the non-gaseous (liquid and/or solid) form and consisting essentially of NiClz and FeClz, and wherein there is more FeClz than NiClz. This starting material is treated in a reaction or sublimation zone, in the presence of a certain amount of metallic iron, to produce a final product which is vaporized FeClz, re moved from the sublimation zone as such, leaving only metallic iron and metallic nickel in the sublimation zone.

[2. Ser. No. 210,433, filed February 10, 1951, now U. S. Patent 2,677,594, issued May 4, 1954, relates to treating a starting material, essentially the same as Ser. No. 160,821, except that in this instance the starting material is introduced into the reaction zone in a solely gaseous state. The reaction and the final products are substantially the same as in Ser. No. 160,821.

0. Ser. No. 160,822, filed May 8, 1950, now U. S. Patent 2,677,606, issued May 4, 1954, relates to the preventing or minimizing of a possible back reaction. The starting material consists essentially of ferrous chloride and metallic nickel. It is desired to separate these materials without permitting, or at least minimizing, a possible back reaction therebetween which would produce nickel chloride and metallic iron. To do this, the starting material is introduced into a reaction or sublimation zone in which metallic iron is present. The starting material as introduced into this zone is in a nongaseous state. The final products are substantially pure ferrous chloride vapor, which is removed from the zone as such, and metallic nickel and metallic iron which remain in the zone.

d. Ser. No. 294,058, filed June 17, 1952 (the present application) discloses a process for treating a starting material substantially the same as in Ser. No. 160,821. This case has been amended so as to preclude the claims reading upon separation of the products of the reaction by vaporization as in Ser. No. 160,821; but in this case the separation following the reaction is effected by withdrawing the metallic nickel produced (by a reaction the same as in Ser. No. 160,821) by withdrawing massive pieces of iron, to which the deposited nickel adheres physically, from the fused bath of the starting materials. Neither the ferrous chloride nor any nickel chloride present is intentionally volatilized. This application is junior to application Ser. No. 160,821, so that the only subject matter claimable therein is subject matter which cannot be supported by the disclosure of Ser. No. 160,821; alSlOthe common subject matter being claimed in Ser. No.

2. Ser. No. 291,816, filed June 4, 1952, now U. S. Patent 2,677,595, issued May 4, 1954, is the first of the three cobalt applications and is the cobalt counterpart of the nickel case, Ser. No. 160,821, distinguishing therefrom by being directed to cobalt and its chloride, rather than nickel and its respective chloride. This case is further distinguished in the degree of purity of the sublimate.

1. Ser. No. 320,835, filed November 15, 1952, now U. S. Patent 2,677,596, issued May 4, 1954, is the cobalt counterpart of nickel case, Ser. No. 210,433. It distinguishes from cobalt case Ser. No. 291,816 in the same way discussed above as to the respectively corresponding nickel cases, while distinguishing from its corresponding nickel case, Ser. No. 210,433, by the diiferences between cobalt and nickel.

g. Ser. No. 321,514, filed November 19, 1952, now U. S. Patent 2,677,597, issued May 4, 1954, is the cobalt case corresponding to the nickel case Ser. No. 160,822. It distinguishes from the other cobalt cases as discussed above in respect to the respectively corresponding nickel cases, while distinguishing from its nickel counterpart, Sci. 1No. 160,822, by the differences between nickel and co a t.

Summarizing the present invention for the purposes of setting forth the novelty therein in respect to the closest known prior art, the present invention comprises treating a fused salt mixture, consisting essentially of FeClz and NiCl2, and wherein there is at least about 50% FeClz by bringing into contact with a molten bath of these two salts some metallic iron, the amount to be at least enough to combine chemically with all the chlorine initially present in the fused salt bath in the form of NiClz; in other words, the stoichiometric proportion or ratio of metallic iron as compared with NiClz for reaction in accordance with the equation:

Preferably, however, in order that the exchange reaction set forth in the equation above be carried on to substantial completion and in a relatively short time, for example, usually about 10 to 15 minutes, there should be at least 1.5 times the stoichiometric quantity of iron required as aforesaid. The temperature at which the molten bath and the iron is maintained should be such that the materials of the molten bath will remain in the liquid state, i. e., from about 1300 F. to about 1800 F. Following the substantial completion of the reaction aforesaid, the ferrous chloride initially present, plus that formed by the reaction aforesaid, may be separated from the remaining solid metallic material by any physical separation.

' The closest known prior art to the subject matter of the present invention is the three patents to Kroll, Nos. 2,396,792-3-4, all granted March 19, 1946. In all these patents the stated purpose was to purify metallic nickel by taking a body of metallic nickel, comminuting it if necessary, so as to convert the body into finely divided powder form, and then treat the powdered nickel .thus prepared so as to eliminate therefrom metallic impurities, one of which was stated to be iron. most cases were present in a total amount of not over The impurities in f a 3 .thismepresentingthe. .totalof all .metallic. impurities and not merely iron. One exception to this was in Patent No. 2,396,792, in an example given in the first column on page ;3,..wherein;thennickelypowderq contained iron. 7

In .all...cases,the reactionrelied uponfor the elimination of .the..metallic .iro'nwas .FeQ-NiCliiNi-I-FteClzi. Prom. thewaytthis'equation was .given andirom .the accompany-f ingdescription in'tne .patentQthis was. acknowledged to be a reversible reaction... 10

In ilatent .No. 2,396,792. the powdered impure. nickel was placed in suspension inla bathloffused potassium chlorideandsodiiim.chloridellin'therproportion of 60/ 40" KClZN'aCl." 1'. Themoltehabathfwas made up in onexexample,"at..least, witl'iItheKClfNi'Cl Tmixture about three 10 times. the'. weight of. the. metal introduced. ilthereinto. Further, in accordance with this. Tpa tent,. nickel chioiidei (NiCl).Lwasladdedi to the-.;moltenv bath, 'so that the resulting.fusedrbath'thus produced would .b'e' 25'% to 50% nickelchloride by weight. The temperatures stated were about.500"C. to'.about.l000.C.. Inithe'most extreme case,that.;is fwhereiniroin was present to lthe extent of about 15% "of the metal aforesaid,'the patentee stated thatin aboutone.hour.90..to 95% of the .ironwouldbe' converted to fer'rous chloride by the reaction above given.

IniKr'ollPatent No. 2,396,793; the bathwas made up substantially as given above except that no nickel chloride as such was deliberately added. Inaccordance with the process disclosed in this patent, however, gaseous chlorine wasbubbled through the bath for reaction with the constituents thereof. This was stated to chloridize some of the nickel, andeither directly or indirectly tochloridize' the iron present: The direct chloridizing of iron would result in ferric chloride. The indirect chloridizing of the iron was efiected by first chloridiz'ing metallic nickel to form'NiClz'," and then permitting the NiClithu's formed to reactwith'metalliciron in'suspension inithe bath in accordance'with'the same equation as given above to reform metallicnickel and to convertthe iron to'Fe'Clz'.

It was further taughtthat if additional stepsof bubbling 4O chlorine throughthei bath'were carried on, FeCla inthe bathWould be chloridized to1FeCl'3,f which in turn could actl'in a secondary manner to chloridize some of the metalliciron in the bathand' be" itself reduced -to FeClz.

The present processdistinguishes from these disclosures, first in that the purpose is to obtain subtantially pure FeClz. As distinguished from this, Kroll either puts in or obtains by his chloridizing action more-NiCli than is disposed'of by the reaction aforesaid, soas to eliminate as much'of the iron ashecan, while-leaving an excess of NiCli'inthe bath. The present purpose is to eliminate a major "part 'and preferably'substantiallyall theNiCl'z," so that all the' remaining Water-soluble constituentswill S be substantially pure ferrous chloride, andpreferably to" have'in contact with the fused bath a substantial amount of excess iron,'which may be'removed as such at the completion of the operation in a manner which'will be hereinafter described:

As a second major diflerence'between the process of' Kroll and the present..process,.- Kfoll-inthe instances of both these patents uses a fused salt bath includinglarge proportions of :such' salts as KCl and 'NaCli In. the present process the' fusedsalt bath contains substantially no KClzor:NaCli"(except possibly as trace impurities), and consists essentially of "Niclz kFeClzl 1 As 'a third major difie'r'ence in the process itself apart from its purpose; the present process starts with -at least about 50% Fe'Clz, while the concentration of this material in any bath contemplatedby Kroll, either before, during, or after the reaction, inaccordance with 'his teachings, would never contain any concentration of ferrous chloride even. approaching 50% i I This last difierence points -up'.. an unexpected action which takes place in accordance withthepresent'process. Since the Fecl is never removed from the bath duringthe continuance of thereaction, the fact that this equation'is a reversible one would indicate that the reaction; particularly, as shown by Kroll, in thepresence .of substantial. amounts of. FeClz, .wouldinever approach .completion from. left:.to right as .givenabove. Furthermore, the]. ratio OfFezClz to NiCl2, as the reactiontproceedsttowards completion, approaches These: two factors v taken in Econjunction'with the; above accepted principles, wouldtindicate that no:resultapproachinga complete cone version of NiClz to metallic nickel and FeClz would be possible. Notwithstandingnthisreasoniug ,it haslbeenm founnd, under the conditions present in accordance with the present process, that substantially complete conversion is in fact eifected, so that in a period of about 10 to 15 minutes (as contrastedpwithKrolls one hour period for relatively incomplete conversion) the concentration of nickel chloride in the; fused bath .is reduced to .such- :a

small amount. as to. be substantially zero, within .the limits of accuracy of the analytical determinationsazvhich. have been made therefor. In other words, this concentration in the remaining'non-metallie--materialis such" thatthe amount of nickel (calculated as metal)-.'therein is lesstha'n 0.03%

Turning now to the details of the present process,-the-' starting material in accordance therewith comprises a molten bathconsisting essentially of NiClz and' FeClz and wherein there is atleastabout 50% by Weight FeClz. This salt bath may be prepared in .any desired manner from any mixtures of these two salts obtained from any source. The salt bathcontains: nothing elsebutthesetwo salts, with the' possiblexception of relatively'small or trace amounts of other materialsf.

In this bath .there .is provided .an amount of ironior reaction therewith. It may be that this iron which must be in metallic form, may in someway be initiallyfpresent.-. with 'theconstituents of the bath prior to the fusionthereof. On'the' other hand, the iron may be introduced into the .ba'thsubsequent tothe fusion of the other constituents. thereof. The iron may 'be in any one or more of the following forms: (a) as one or more solid massive bodies, for example, one or more iron rods extending into-the. bath, (b) as a solid material providing a relativelylarge surfaceper unit of weight, such, for example, asa body of steel wool or a body ofs'ponge .iron, .or (c) iron'in relatively'finely divided powdered 'formirrespective of the manner of preparation or..sourcerof that powder... Anymixtures of the several forms of iron may be used if desired;

As to the amoun-t'of iron which .must be present, ini. accordance with the present invention, there is required at least the stoichiometric equivalent amountof. iron required for chemical reaction in accordance with..thel.. equation given above with all the; chlorine initially 'pres-. ent in the bath'in the formof nickel chloride From the. pointof 'v'iewof the preferredpractice of the process, howeverythe amount of iron is preferably substantially greater than the mere equivalent or stoichiometric amount and'is at least about 1.5 times this 'stoichiometric or.v equivalent amount. On'the' other hand, "there is no defi niteupper limit for the amount of .ironwhich may. be l present: Thus; if amount of iron were present, for". example, in the' form of one or more large masses, many 7 times the amount necessary for. conversionas aforesaid,"

the process is fully'operative. The practical lirnit,lthe'refore, is dependent upon the convenience of operationand. thesizeofthe equipmentz'iniwhich the'lprocess. is 'to be carried'on; Conceivably; also. the process could 'becarried on'in an iron tanker container ofsome kind, so.- that the iron would be provided by :the container in which. the processis carried on. i This, however,.is not usually? desired aszthe process consumes some of the .iron, so that the container would have a relatively sho'rtlif'e Iin.. repeatedly carrying on the process.

The temperature for the reaction. is lanytcmperature. within: the general range'of' aboutii1300"F.' 'to about; 1800"F. These temperaturelimits are. chosen as follows; Thelow limit ofaboutr1300F.' is a point..about or just above'the melting point of the saltsmaking' .up the bath-aforesaid. Thus, at least this. temperature is required" in orderthat the bath-be. kept in a molten state, which is, of;:course, onexof the essential factors. of the present invention." The-highlimit again'is dick. tated by therequirement that .the bath'be kept molten this hightemperature limitbeing about or slightly below the boiling point of mixtures .of ferrous chloride and... nickel chloride at 'atrnosperic'pressure. Itiis'notedin'... this connection that-the boiling pointofa mixture 'ofafer rous chloride and. nickel chloridef'is .above'. the' boiling points. of .each .of .thesematerials: alone. 1 Oiitherother. hand,.if for some reasonit were. desired that the .high temperature'limit be. higher or lower,.this could bevef-f' fectedby some control of the absolute pressure 'eifective s: on the molten bath.-during-the.:operation,=-:which=willzin.

turn. control .the. :boiling :pointrithereofrainxa I way which-h.

will be obvious to those skilled in the art. Thus, if

it were desired to conduct the operation at some higher temperature, for example, 2000" F., sufficient super-atmospheric pressure could be employed within a closed reaction chamber or zone to keep the components of the molten bath liquid even at such a relatively high temperature. In general, the temperatures are such that the constituents of the bath remain in liquid form and do not volatilize to any substantial extent.

Due to the fact that ferrous chloride and nickel chloride are both subject to oxidation at relatively high temperatures, it is practically necessary that a non-oxidizing atmosphere be maintained above the molten bath during the present process. Such an atmosphere may conveniently be nitrogen.

The time necessary for conversion of the nickel chloride to metallic nickel and ferrous chloride in accordance with the present invention, has been found to be quite short, in the order of magnitude of to minutes in most cases, as will appear in greater detail from the following examples.

No particular theory of operation of the present process tending to explain how the apparently anomalous results are in fact obtained, as compared with what would be expected from the teachings of the Kroll patents and from mass action principles, can be given herein as these explanations are not known at this time. It can only be supposed, however, that the unexpected results must be due in a large measure at least to the actual differences between the present process and the processes specifically disclosed by Kroll and outlined above. tion, it is noted that Kroll Patent No. 2,396,794 does not relate to liquid phase operations at all, but rather is restricted to solely solid phase reactions.

Following the substantial completion of the reaction aforesaid, the ferrous chloride originally present, plus that formed by the reaction, is separated from the remaining solid metallic materials. If the iron is introduced as one or more massive bodies, such as rods, the remaining portions of these rods, to which the deposited nickel will adhere, may be lifted bodily from the bath. In the event that the iron is introduced into the molten bath in the form of a body of steel wool or of sponge iron, the remainder of such body respectively with deposited nickel adhering thereto may be lifted out of the molten bath. These expedients may be termed physical separation.

The practice of the present invention and the practical limits thereof are further illustrated by the following examples:

Example I than the amount of iron that would be theoretically necessary to react with all the chlorine present in the molten mixture in the form of NiCl2. A charge, consisting of molten FeClz and NiClz in the ratio of parts by weight of FeClz to one part by weight of NiClz, was maintained at a temperature of 1500 F. in a protective atmosphere of nitrogen. Suificient iron in the form of steel wool was immersed in this molten bath to provide in contact with the molten material, 1.5 times the amount of iron theoretically necessary to react with all the chlorine present as NiClz. At the end of 15 minutes, the steel wool was removed from the molten bath and was found to have exhausted the nickel content thereof as the bath was found to be substantially free of NiClz. The bath, when analyzed, had a nickel content of less than 0.03% which was the limit of error of the analytical method used.

The effect of providing sufficient metallic iron in contract with the molten material upon the degree of completion of the desired reaction is seen by comparing the above result with the results obtained by providing in contact with a molten bath, having the same initial composition of FeClz and NiClz, and at the same temperature, only suflicient metallic iron to equal the amount theoretically required to react with the chlorine present as NiClz. It was found in this case that, even after 120 minutes of contact between the metallic iron and the molten mixture, this mixture, which originally contained 3.3% NiClz, still contained about 0.29% NiClz.

Thus, if the required purity of the FeClz product of the process permits of 0.29% NiClz, then the stoichiomet- In this connec- 6v ric amount of iron may be used; while if a higher purity FeClz is required, a greater proportionate amount of metallic iron should be used as aforesaid.

Example 11 The desired exchange reaction between metallic iron and molten NiClz may be brought to substantial completion, in a relatively short time, by the method of the present invention, at any temperature within the range in which the mixture of FeClz-NiCh being treated is in the molten state. When a molten mixture of FeCl: and NiClz, containing 30 parts by weight of FeClz to one part by weight of NiClz, was maintained at a temperature of 1300 F. (which is just above the melting point of such a mixture of chlorides), and sufficient metallic iron in the form of steel wool to equal 4 times the stoichiometric amount of iron theoretically necessary as aforesaid was maintained in contact with this chloride mixture, it was found that the molten material was susbtantially exhausted of its nickel content (as measured by the same test referred to in Example I) in 15 minutes.

Another mixture of these chlorides in the same proportion was treated in the identical manner at a temperature of 1800 F. It was found that the nickel content was substantially exhausted as aforesaid after 10 minutes of reaction time.

Example 111 The metallic iron used to react with the nickel chloride may be provided in any convenient form, such as steel wool, which was used in the two examples given above. However, substantially identical results are obtained when the iron is provided in other forms. For example, it was found that when sufiicient finely divided iron powder to make up 4 times the stoichiometric amount of iron theoretically necessary to react with all the chlorine present in the molten mixture in the form of NiClz was added to a molten mixture of FeClz and NiCl2, containing these chlorides in the proportion of 30 parts by weight of FeClz to one part by weight of NiClz, at a temperature of 1500 F., substantially all of the nickel content of the molten bath was exhausted as aforesaid in 15 minutes. When the same amount of metallic iron in the form of a solid iron rod was immersed in a chloride mixture of the same composition at 1800 F. for 10 minutes, it was found again that the nickel content of the molten bath had been exhausted as aforesaid; but that this time the metallic nickel had deposited in the form of a coating on the iron rod. It was found that the deposit on the surface of the iron rod appeared to be, at least in part, an iron-nickel alloy.

Example IV Although the invention finds most of its application in the treatment of the FeClz-NiClz mixtures, which are relatively poor in NiClz, it is equally applicable to compositions containing as much as 50% NiClz by weight. In this case somewhat more time is required substantially to exhaust the nickel content of such a rich bath. Thus, when a molten mixture of FeClz and NiClz, containing these chlorides in equal parts by weight, was contacted with an iron rod equivalent to four times the amount of iron theoretically necessary to react with all the NiCl2 of the mixture at a temperature of 1800 F., it was found that after 15 minutes the chloride bath still contained about 2.1% NiCl-z. However, when the reaction was carried on for 30 minutes, it was found that the nickel content of said bath was completely exhausted as aforesaid.

While we have described our process in general, and have set forth in some detail the chemical and physical riquirements thereof, it is recognized that the process may be operated by the substitution of such equivalents as will suggest themselves to those skilled in the art from the foregoing disclosure. We do not wish to be limited, therefore, except by the scope of the appended claims, which are to be construed validly as broadly as the state of the art permits.

What is claimed is:

The process of separating ferrous chloride, substantially free of NiClz, from a starting material containing both NiClz and FeClz, and in which there is a greater amount of FeCl;; and NiClz, which comprises introducing said material into a reaction zone in a non-gaseous state, providing suflicient metallic iron in solid massive form in rsaidl'zone :andlin; contact witliLthElnon-gaeeons .mate-l rial therein to as suret hlat threis tpresentlhtyleashsufficient metallic iron to reactwith' all 'the' chlorine which is present in said zone in the form of NiClz to form FeCl2,=.maintaining.lhev.material inusaidzone. within vthe 5 state.

temperature, range of 'abo'uth600 'CIT up. to biit below thebdiling'.pointoffecl"atvtheLpressurezexisting in said 1 zone and .for v21 .time andmundenconditions such "was to permitfthe completion of Ythe reaction between all 'the' NiCliprescnt 'withflthcimetallic"iron toform n-letzzllic i 2,396,792 Kfoll Min; 19;;1946 w nickelv and. :FeCl2,\themetallic/nickel -ilepositin'g upon 2,396,793' Kr'oll Ma1". 19, .1946 the solid massive iron, landuseparating the metallic nickel 2,396,794 Kroll .rM'arr 19, 1946 r References Citedin the file of this; patent: V

UNITED 'STATES PATENTS 

